As indigenous woodland trees, decorative landscaping specimens, street trees or hedges, Acer varieties are highly adaptable. Leaving aside the well-known shrubby ornamental Japanese maples (A. palmatum), there are about 150 species, plus many cultivars.
With its fine autumn colour and elegant shapes, Acer has one of the best ranges of ornamental leaves. A typical Acer leaf has five palmate lobes but they can have anything from three to 13 lobes, or none. What identifies them is the winged fruits, commonly called keys, which are decorative in their own right.
One of the most striking at this time of year is A. rubrum ‘October Glory’ Award of Garden Merit (AGM), which in a good year outshines all others. Although recommended for acid soils, they colour up well in alkaline soils too. Before turning, the often colourful foliage ranges from shades of green to the bright yellow of A. cappadocicum ‘Aureum’ AGM, or the plum red of A. platanoides ‘Crimson King’ AGM. It can also be strikingly variegated.
The striped bark types grown as multi-stemmed shrubs are gaining in popularity as they are particularly suited to smaller spaces. Several are termed snake bark maple, including A. capillipes AGM. This and the striped maple, A. pensylvanicum AGM, look good all year and have more interesting autumn leaf colour than birches.
More often grown as a single specimen tree is the best-selling paper-bark maple, A. griseum AGM. It is a slow-growing, medium-sized tree, grown for its copper-coloured peeling bark.
Acer flowers are generally unexciting, although there are exceptions, such as A. platanoides ‘Schwedleri’ AGM, which boasts attractive sprays of greenish-yellow blossom in spring.
Some acers can be pollarded, while the native field maple, A. campestre AGM, can be pleached or grown as a hedge. It is also beneficial to wildlife, as are the Norway maple, A. platanoides, and the sycamore, A. pseudoplatanus — both naturalised in the UK.
The genus also offers a range of street trees, such as A. platanoides ‘Globosum’, with its compact, dense green crown.
Acers grow well in a rich, moist, well-drained soil in sun or partial shade. The yellow-leaved or variegated varieties prefer partial shade, which stops the leaves from scorching.
The species are propagated by seed; the cultivars are layered or grafted for uniformity. They are susceptible to a number of pests: aphids, scale, honey fungus, caterpillars and mites, which may cause knobbly galls. They are also prone to Verticillium wilt, but they are not usually treated, often because they are too large.
What the specialists say
Steen Berg, owner, Yorkshire Plants, North Yorkshire I believe a future trend will be multi-stemmed Acer, as its ornamental bark has a contemporary feel and great autumn colour.
The trees are not really expensive — costing around 20 per cent more than a normal tree. We sell multi-stemmed A. pensylvanicum Award of Garden Merit (AGM) with green and white striped bark, and A. davidii ‘George Forrest’ AGM, which has red bark with white veins.
I’d also recommend some of the field maple cultivars which are really underused. They have a classic A. palmatum leaf — small and delicate — but are less tender, don’t get Pythium root rot, and can also be cut down to any sort of size. A. campestre ‘Carnival’ is a variegated one with a white and pink edge to its green leaf, and A. campestre ‘Postelense’ is a golden-leaved form.
One of my favourite medium-sized acers for the garden is A. cappadocicum ‘Aureum’ AGM because of the snake-like markings on its young bark and its golden leaf, which is pinkish when young.
Brian Fraser, sales and business manager, Oakover Nurseries, Kent We’re seeing demand for acers increase because they give a lot of colour and people are looking for something a bit different. Previously they’ve gone for birches but most of those have brown or white stems, whereas snake barks will give you a green or red striped stem.
Acer griseum AGM is nice because it has lovely red, peeling bark and is naturally more of a bush-type plant than a straight tree so has lots of character. It’s unusual to have a tree with peeling bark other than birches.
We also sell A. davidii ‘George Forrest’ AGM, which has reddish patterned bark. Given quite a bit of light and space and a light soil it makes a good garden specimen.
We also sell Norway and field maples as feathered trees, and they’re used by the amenity sector for office blocks or schools. A. campestre AGM can be included in a native hedging mix and A. platanoides AGM is grown as a tree. They may get mildew but it’s not something to worry about.
Cleve West, landscape designer, Surrey For my Chelsea garden, I used A. campestre AGM, pollarded in an elliptical shape over a seating area. The nice thing about them is that they get quite an individual rustic look when pollarded, and become craggy and amoebic-shaped when they mature.
Recently I’ve planted a field maple hedge in a teaching garden at RHS Wisley. You normally see it as a mixed hedge but I like the leaf shape so much I’ve used it on its own.
Acers are beautiful trees, but often it’s hard to find the right place for them. Most of the gardens I design are in towns and they are just too big.
Species and cultivars
• A. campestre Award of Gardening Merit (AGM)* is a compact woodland tree growing to 6m tall or grown as a shrub or in mixed hedges. It has five-lobed deep-green leaves that turn yellow in autumn.
• A. campestre ‘Carnival’ has a variegated white and pink edge to its small, delicate leaves.
• A. campestre ‘Postelense’ has golden leaves.
• A. capillipes AGM is a popular variety with grey-green bark and vertical white stripes. It is a spreading tree, growing to 10m, or is sold multi-stemmed to show off its bark. It has three-lobed dark green leaves turning red, orange and yellow in autumn.
• A. cappadocicum ‘Aureum’ AGM is a medium-sized tree reaching 20m tall with a 12m spread. The foliage has five to seven lobes and is lime-green or yellow, fading as it ages.
• A. cappadocicum ‘Rubrum’ AGM has eye-catching, wine-red foliage.
• A. davidii ‘George Forrest’ AGM has green and white streaked bark. It has large, dark green leaves and pink-brown fruits in autumn.
• A. davidii ‘Serpentine’ AGM has green and white streaked bark against dark purple bark.
• A. griseum AGM is widely grown as a specimen tree for its unique coppery brown peeling bark. It is a slow-growing, spreading tree reaching 10m or more with orange-red leaves.
• A. grosseri var. hersii AGM has streaked bark and green leaves that turn orange or yellow in autumn.
• A. japonicum ‘Acontifolium’ AGM is a 10m-tall tree or shrub. It has deeply lobed green leaves, which take on bright autumn hues.
• A. japonicum ‘Vitifolium’ AGM has large, shallowly lobed leaves that turn red and orange in autumn. Strong sun may scorch the foliage.
• A. negundo ‘Flamingo’ has pale pink, variegated, pinnate leaflets that may turn white. It is fast growing and responds well to pollarding. Left as a tree it grows to 7m.
• A. pensylvanicum AGM is a broadly upright tree growing to 12m by 10m. It has bright green obovate leaves, which are bright yellow in autumn, and stripy green and white bark.
• A. platanoides AGM* is a large, fast-growing tree, maturing to 25m tall with a 16m spread. It has five-lobed, light green leaves, turning yellow or red in autumn.
• A. platanoides ‘Crimson King’ AGM* has dark purple, palmately lobed foliage that turns red and orange in autumn. It grows to 18m by 15m.
• A. platanoides ‘Globosum’ is often planted as a small street tree. It has a dense crown of green leaves.
• A. platanoides ‘Schwedleri’ AGM has purple-red leaves that turn orange-yellow in autumn. It has purplish yellow flowers before the leaves.
• A. pseudoplatanus grows to 20m by 16m. Tolerant of pollution and exposure, it is often planted in urban areas and is a prolific self-seeder.
• A. pseudoplatanus ‘Brilliantissimum’ AGM is a compact maple, growing to 4.5m with a 3m spread. New foliage is shrimp-pink in colour, aging to green, then yellow in autumn.
• A. rubrum is a large tree growing to 20m with a 15m spread. Its green leaves turn red and yellow in autumn. It has red flowers and winged fruit.
• A. rubrum ‘October Glory’ AGM offers great autumn colour, with glossy foliage turning red, orange and yellow.
• A. rufinerve AGM has green and white striped stems and green leaves that turn red and yellow in autumn.
• A. shirasawanum ‘Aureum’ AGM is a bushy shrub or tree growing to 6m with bright yellow leaves that redden in autumn. Red-purple flowers come out in spring.
*Included in the HTA’s Top Plants for Amenity Landscapes